How did Christianity ultimately change the Roman Empire?

Ultimately, the major change was that Christianity became the official religion of the empire, doing away with centuries of traditional ways. Edward Gibbon argued that Christianity also helped destroy the empire, but his view is no longer accepted by most scholars.

Gibbon argued that Christianity made Romans less vigorous. He argued that it made them focus on the next life and therefore neglect things like the defense of Rome.

Historians can agree today that the adoption of Christianity under Constantine changed Roman society. It led to Constantine abolishing the pagan temples and appropriating their wealth. It led to the abolition of the gladiatorial games. It (arguably) led to other such laws, such as a ban on infanticide, that were more humane from the modern point of view than Roman laws were before. In these ways, Christianity can be said to have made Rome less brutal in addition to simply changing Roman society by doing away with the connection between the government and the old pagan religion.